Floor scrubbing machines are widely used to clean the floors of industrial and commercial buildings. They range in size from a small model which may clean a path ranging from perhaps 15 inches up to 36 inches wide controlled by an operator walking behind it, to a large model cleaning a path as wide as five feet controlled by an operator riding on the machine. In general, these machines have a wheeled chassis which contains, in addition to power and traction drive means, a tank to hold clean scrubbing solution and a tank to hold soiled solution recovered by a vacuum squeegee system from the floor being scrubbed. A scrub head is attached to the chassis by an articulated linkage system, and may be located in front of, under or behind the chassis. The scrub head contains one or more rotating scrub brushes and means to power them. These brushes may be either flat disc brushes that rotate about vertical axes or they may be cylindrical brushes rotating about horizontal axes. Both systems have their advantages and disadvantages, and both are widely used.
We are concerned here with scrubbers that use two counter-rotating cylindrical brushes, which is a common construction in the industry. The brushes are set parallel to each other and are closely spaced, with their axes of rotation being horizontal and transverse to the longitudinal axis of the machine. A major advantage of this configuration is that the cylindrical brushes, while scrubbing the floor, act cooperatively to also sweep up small items of loose debris that may be on the floor being scrubbed and deposit them in a debris tray. They are thus prevented from getting into the vacuum squeegee, where debris items may lodge under the squeegee lip and hold it off the floor, thus causing water streaks. Disc brushes do not have this sweeping capability. A good description of a prior art scrubber using two cylindrical brushes may be found in U.S. Pat. No. 3,702,488.
Cylindrical brushes commonly have some sort of drive means on one end to rotate them. Hydraulic motors mounted in line with the brushes have been used for this, as described in the above referenced patent. As described there, the hydraulic motors may be at least partially inserted into the hollow cores of the brushes. However, the hydraulic supply lines require some space outside of the brushes, which limits how closely the surrounding scrub head housings can be fitted at that end of the brushes. This in turn limits how close to a wall the machine can scrub on that side of the scrub head.
Cylindrical brushes are also commonly powered with electric motors mounted on top of the scrub head which drive the brushes through chain or belt drives. These belts or chains also take a certain amount of space at one end of the brushes, so again the machine is limited as to how close to a wall it can scrub on that side of the scrub head.
Many of these prior art scrubbers have the drive means placed on the same end of both brushes so that their opposite ends, which may be termed the idler ends because they are supported by idler bearings, can be closely shrouded to allow one side of the scrub head to scrub close to a wall. However, the weight of these drive motors, located as it is on the same end of both brushes, requires that some counterbalancing means be provided to obtain an even weight distribution of the scrub head on the floor. Generally a spring system is employed. Whatever is used adds to the cost and complexity of the machine.
There is thus a need for a scrubber using two counter-rotating cylindrical brushes with their known advantages, but which in addition permit scrubbing as close to a wall on both sides of the scrub head as current cylindrical brush scrubbers can scrub only on the side of the scrub head which doesn't have the brush drives. A further advantage would be achieved if the weight of the scrub head could be inherently balanced from side to side, thus eliminating any need for a counterbalancing means.